The present invention relates to a toner and a production method of the same.
With response to energy saving in recent years, enhancement of fixability of toners has been investigated. In order to enhance the fixability of the toner, it is preferred that the melt viscosity of a resin component, which composes said toner, is lowered. However, when the melting temperature of said resin component is excessively low, the storage stability of said toner tends to be degraded. Accordingly, development of toner has been demanded in which fixability and storage stability are both within acceptable ranges.
As techniques to enhance the fixability of toner, it is known that microdomains are formed employing substances such as crystalline polyesters and the like together with amorphous polymers. Japanese Patent Publication Open to Public Inspection Nos. 63-57855 and 63-27856 disclose toner in which polymers, which are prepared through chemical graft- or block-polymerization of amorphous vinyl polymer with crystalline polyester, are employed as the resin component. However, though such a technique is employed, it is difficult to decrease melt viscosity by employing the crystalline polyester, and the enhancement of fixability is limited.
In order to enhance the fixability of toner, it is necessary that crystalline materials uniformly exist at a definite ratio in toner particles while maintaining a domain structure at a certain level. However, a method has not yet been discovered which allows crystalline materials to exist in toner particles in such a state (domain structure). For example, even though incorporation of crystalline materials into toner particles is attempted by employing a mix-kneading method, said crystalline material melts due to the heat produced during mix kneading. As a result, it is impossible to form the domain structure, and it is currently impossible to enhance the fixability by incorporation of crystalline materials into toners.
It is an object of the present invention to provide a toner which has a wide fixable temperature range as well as excellent fixability, and a production method of the same.
The other object is to obtain a toner having sharp charging distribution, and excellent in image quality and resolving power.
The toner of the present invention is obtained by fusing or coalescing fine resin particles comprising amorphous polymers and crystalline materials in a water-based medium.
Further, said crystalline materials preferably have a melting point of 60 to 130xc2x0 C., a number average molecular weight of 1,500 to 15,000, and a melt viscosity at the melting point +20xc2x0 C. of not more than 100 dpaxc2x7s.
Toner of the present invention is obtained in such a manner that fine resin particles are obtained by emulsion polymerizing a radical-polymerizable monomer solution prepared by dissolving crystalline materials, and the resulting fine resin particles are fused or coalesced in a water-based medium.
Further, said crystalline materials preferably have a melting point of 60 to 130xc2x0 C., a number average molecular weight of 1,500 to 15,000, and a melt viscosity at the melting point +20xc2x0 C. of not more than 100 dPaxc2x7s.
The inventors of the present invention have conducted investigations regarding the realization of fixability enhancement effects in a toner by employing crystalline materials. As a result, it was discovered that a toner obtained by incorporating crystalline materials into said toner employing a specified production method fully exhibits said effects.
In the present invention, crystalline material is previously incorporated into fine resin particles and the resulting fine resin particles are then fused or coalesced. As a result, it is possible that the presence of said crystalline material is varied to a certain domain structure.
The production method of the present invention is one in which a toner is formed by fusing fine resin particles comprised of amorphous polymers, for example vinyl polymers, and crystalline materials. By employing said method, it is possible to subject fine resin particles themselves to function as a so-called microdomain structure, and thus it is possible to enhance the fixability of the obtained toner.
In order to incorporate crystalline materials into fine resin particles, first, a uniform solution is prepared by dissolving crystalline materials in radical-polymerizable monomers composing amorphous vinyl polymers. Subsequently, the resulting solution is emulsify dispersed into a water-based medium, and polymerization is carried out in the system to form fine resin particles. As a result, as the polymerization proceeds, crystalline materials are deposited in the interior of the fine resin particle, and thereby the desired domain can be formed. By utilizing this method, it is possible to form a uniform domain structure. Further it is possible to control the diameter of the fine resin particles so as to form a relatively uniform particle diameter distribution. Thus, it is possible to uniformly disperse the crystalline materials into the toner. Further, during the incorporation of crystalline materials into the toner, excessive heat energy is not provided. As a result, crystalline materials do not melt. Thus the domain neither increases nor decreases, and even in the worst case, neither is the domain dissolved in the resin, nor does it disappear.
The toner of the invention has narrow and sharp toner size distribution and uniform toner shape. Accordingly the toner has narrow and sharp charge distribution, which gives image with high quality, high resolution and good gradation.